Separation of iron from titaniferous iron ores



United States Patent O SEPARATION OF IRON FROM 'IITANIEEROUS IRON ORES John M. Daubenspeck, Westfield, and Robert.D.Toon1ey, North Plainfield, N. 1., assignors to National Lead Company, New York, N. Y., a corporation of New Jersey .No Drawing. Application November 3, 1951, Serial No. 254,814

4 Claims. -'(Cl. 751) production of substantially pure titanium dioxide wherein a gaseous oxidizing agent and titanium tetrachloride are reacted with a titaniferous iron cm in the absence of a reducing agent.

Other objects and advantages of the invention will be evident from .the following description thereof.

The present invention in its broadest aspects contemplates .a unitary process for separating iron from titaniferous iron ore by treating it with a gaseous oxidizing agent and titanium tetrachloride so as to form vaporous ferric chloride and a substantially pure titanium dioxide residue which is susceptible to additional chlorination .for the production of titanium tetrachloride. More specifically, the'improved and integrated process of this invention comprises the oxidation and chlorination of a titaniferous iron ore by a mixture of titanium tetrachloride and chlorine to form a titanium residue substantially free of iron.

The term oxidation as used herein shall be understood to mean a process in which the positive valencesof an atom is increased and hence is comprehensive of processes wherein the positive valence ofan atom is increased byreaction with air, chlorine or other oxidizing agents.

' Separation of Z'ILOIL by treatment with titanium tetrachloride One of the customary processes for 'separatin'g'titanium values from titaniferous material has been by chlorinating comminuted titaniferous materials at relatively low temperatures andin the presence of carbon or other reducing agents to produce a gaseous mixture of titanium tetrachloride and iron chlorides, i. e. ferric and ferrous chlorides; andsubsequently separating the gaseous mixture into its components to obtain a relatively .pure form of titanium tetrachloride.

This and similar procedures entail variousdifliculties not thejleast of which is that .of separating the iron chlorides from the gaseous mixture of iron and titanium chlorides. Some degree of separation of these gaseous com ponents of the mixture may be effected by fractional condensation due to the normal tendency of ferric chloride to condense from the vapor state directly to the solid state while the ferrous chloride condenses to form/aliguid. However, since the liquid ferrous chloride .tends to coat the solid reactants and thus cause. objectionable plugging and low operation :efficiences, it .is highly desirable .to convert all of the iron values to the volatile ferric chloride state.

Other methods have been proposed for separatingiron from titaniferous materials in the absence of a reducing agent'in an elfort to .form volatile iron chlorides 'which may .be removed as vapor without effecting 'volatilization of the "titanium chloride, but as far as is known there. is no commercial application of these processes.

The present invention is based, in part, upon the dis- 1 covery that titanium tetrachloride may be used successfully to separate iron from the titanium values of titanifer- .ous iron ore. Accordingly, an object .of the .invention is to ,provide .an improved method for separating iron from .titaniferous materials. A further object of the invention .is toprovide an improved method forseparatingiron from titaniferous materials so as to produce .efliciently, substantially pure titanium values conveniently and -on a commercial scale. A further object of the invention is '10 provide an improved method .for treating .titaniferous .iron .ore whereby the iron .in the ore .may .be separated from the titanium values without the .diificulties attending the use. of a carbonaceous reducing agentandin .a manner to insure the production of a granular titanium .residuesusceptible to chlorination for the production of titanium tetrachloride. A still further object. of the invent'ionis to'provide an improved method for the commercial and chlorine In a preferred embodiment of the invention, .the separation of the iron from the titanium values in the ore is accomplished by treating Iaw (unoxidized) orewith a mixture of volatilized titanium tetrachloride and chlorine in the absence of carbon or equivalent reducing agent. Although the exact nature of the reaction of volatilized titanium tetrachloride and chlorine with the. ore is not exactly known, two possible explanations of the reaction are o'ifered; the one being that the chlorine serves as an oxidizing agent for converting some of the ferrous oxide values to ferric chloride and ferric oxide While the titanium tetrachloride reacts with the ferric oxide values thus formed and with the original ferric oxide values in the ore to convert these iron values to volatile ferric chloride, the titanium tetrachloride also reacting with any remaining ferrous oxide to form ferrous chloride which, in turn, .is acted upon by the free chlorine .to form volatile ferric chloride. The second proposed explanation is that the titanium tetrachloride converts theiron-oxide values of the ore to ferric and ferrous chlorides .and'that the chlorine oxidizes the ferrous chloride values to form ferric chloride. In any event, substantially all of the .iron values escape from the reactor as volatile ferric chloride thereby leaving a residue of substantially pure granular titanium dioxide. In this connection experiments have shown that when volatilized titanium tetrachloride alone is used .to chlorinate the iron or raw ore, -i. e. unoxidized tore, the reaction soon slows down, the bed becomes frozen and the gas flow is reduced to channeling through the bed. It is important, therefore, that ,a mixture of titanium tetrachloride and chlorine be used with raw .ore toinsure the. commercial success of the process. Theterm .granular as applied to the titanium dioxide product -of the reaction .is used to connote a material consisting of separate and distinct particles of appreciable size such as may be susceptible to chlorination; and :to distinguish over an amorphous product whichmay not 'be chlorinated at all or only with relatively great difficulty.

The titaniferous ore to be treated is a raw ore comprising a mixture of iron and titanium compounds in subdivided form, and is preferably treated .in .a fiuid-solid system by a mixture of titanium tetrachloride and chlo- .rine gases in the absence of a reducing agent and at :an

is to initially form a bed of ore in a reactor by charging the reactor with a predetermined amount of subdivided titaniferous iron ore which has been beneficiated by the removal of siliceous gangue including iron oxides. To initiate the reaction, volatilized titanium tetrachloride, mixed with chlorine is preheated to a temperature between about 250 C. and about 350 C. and introduced into the reactor beneath the bed to flow upwardly therethrough and form a fluidized bed, that is to say, a bed of ore in which the individual particles of ore are held in a state of dynamic suspension, the suspension being maintained preferably by a regulated upward flow of the gases. In forming the fluidized bed in the reactor the velocity of the gases flowing upwardly through the bed must be sufficient to hold the particles of ore, or equivalent material, in dynamic suspension, but not so great as to force these particles upwardly out of the reaction zone of the reactor. Satisfactory dynamic suspensions have been obtained with space gas velocities from about 0.3 foot per second to about 1.0 foot per second using ores the particles of which fall within the size range of an average ilmenite beach sand which may be of the order of 20-200 mesh.

Although the fluid solid system described is satisfactory, it will be understood that other methods of carrying out gas phase-solid phase reactions are contemplated within the purview of the invention; and that while a static bed system is generally slower and subject to channeling, the process of this invention may, nevertheless, be carried out by this method.

To the aforementioned fluidized or dynamic bed is added additional raw titaniferous ore, which has been preheated to between about 300 C. and about 400 C. in order to prevent lowering of the temperature of the reaction zone and condensation of the volatile ferric chloride as the raw ore is fed downwardly into the fluidized bed.

Although the exact mechanism of the reaction between FeO, C12 and TiCl4 is not known, the overall results of these reactions may be represented by the equation:

2FeO+Cl2+TiC14 ZFeCla-l-TiOz (Equation 1 In this reaction the TiCl4 reacts with the ferric oxide values according to the following equation:

2Fez0s +3TiCl4- 4FeCl3 3TiO2 (Equation 2) The chlorine reacts with the ferrous oxide values in the ore and with the ferrous chloride values formed by reaction of the TiCl4 with the ferrous oxide values in the ore to form ferric chloride. The conversion of the iron values in the ore to volatile ferric chloride may be 90% or higher while substantially all of the volatilized ferric chloride escapes from the fluidized bed of the reactor thereby leaving a substantially pure titanium dioxide residue. i

In accordance with these two equations 0.494 part of chlorine and 1.32 parts of titanium tetrachloride will be required for each part of ferrous oxide present in the ore; and, in addition, 1.78 parts of titanium tetrachloride will be required for each part of ferric oxide in the ore.

The amount of titanium tetrachloride used is preferably the theoretical amount required to react with the iron in the raw material and although a slight excess of titanium tetrachloride could be employed to insure high conversion of the iron to ferric chloride, large excesses of titanium tetrachloride are to be avoided, since this procedure involves loss of titanium tetrachloride and concurrent contamination of the volatile ferric chloride product with titanium tetrachloride.

The amount of chlorine used should be sufficient to oxidize the ferrous oxide values in the ore as well as any ferrous chloride produced by reaction of the titanium tetrachloride with the ferrous oxide, and satisfactory results have been obtained when the stoichiornetric amount of chlorine has been used. In actual practice, however, it seems desirable, when oxidizing said chlorine to employ at least excess chlorine over the stoichiometric proportions to secure rapid and complete reaction. Any

for each part of FeO present in the ore.

unreacted chlorine may be subsequently collected and recirculated through the dynamic bed of the reactor for oxidizing additional ore. On the basis of the preferred molar ratios of titanium tetrachloride to chlorine being from 1:1 to 1:3 then from 2.7 to 0.9 parts titanium tetrachloride are used with 1 part chlorine by weight depending upon the amount of ferrous oxide present in the titaniferous ore.

In general the reactions by which the iron values in the titaniferous iron materials are converted from oxides to chlorides occur over a temperature range from about 500 C. to 1200 C. For titaniferous materials of the order of less than 325 mesh and in which substantially all of the iron values are in a reduced or ferrous state, the conversion of the oxides by oxidation and chlorination to ferric chlorides occurs at the lower end of the temperature range, the preferred reaction temperature from the standpoint of high efficiencies being in the range from about 700 C. to 900 C. On the other hand, where the titaniferous materials contain both ferrous and ferric iron values, generally higher temperatures are used for an eflicient conversion of the oxides by the process of this invention, the preferred range being from about 850 C. to 1050 C.

It has been discovered that when maintaining a fluidized bed of granulated ore by an upward flow of gas at a rate of between 0.3 foot and 1.0 foot per second the titanium dioxide is not carried up out of the reactor with the volatilized ferric chloride but accumulates as a residue in the fluidized bed. This unexpected phenomenon may be attributed to the fact that the particle size of the chlorinated ore remains substantially unchanged, or at most, suffers but slight decrease in size. Apparently the displaced iron atoms of the ore are replaced by titanium atoms with the result that the lattice structure remains substantially unchanged. Hence, while the ferric chloride formed by chlorination of the ferric oxide is volatilized from the bed, the titanium dioxide, being non-volatile and occluded in the residue remains in the bed and may be subsequently chlorinated in the same reactor or transferred to a separate zone where the titanium dioxide particles may be suspended in the presence of a mixture of carbon and chlorine gases to produce titanium tetrachloride. Chlorination of the residue, i. e. enriched titanium dioxide, by either the batch process or continuous reaction process has established that the enriched titanium dioxide may be chlorinated with at least equal and even greater facility than natural rutile ore.

The volatilized ferric chloride may be removed from the reactor by collecting the chloride in a separate zone and decomposing the chloride by the introduction of oxygen to form iron oxide and chlorine gas.

Although the foregoing description relates, in particular, to the oxidization and chlorination of a raw (un oxidized) ore, the process of this invention is applicable also to titaniferous materials in which substantially all of the iron values are in the reduced or ferrous oxide state.

Separation of iron by oxidation and subsequent treatment with titanium tetrachloride While the treatment of raw (unoxidized) titaniferous ore by an admixture of titanium tetrachloride and chlorine is preferred, it is within the purview of the invention to treat a titaniferous ore by preliminarily oxidizing the raw ore and thereafter chlorinating the oxidized ore.

The oxidation of the raw ore may be effected in any one of several accepted ways, such as, for example, by roasting the ore in the presence of air. Where air or other oxygeniferous gas is used, the amount used must be suflicient to convert substantially all of the ferrous iron present in the ore to ferric iron according to the following equation:

2FeO+ /2O2 Fe2O3 (Equation 3) Thus a minimum of 0.111 part of 02 must be supplied In actual practide it-"may be desirabl'e to depart fromutheeitact stol chiometric proportions and to" use-arlarge'excessr'ofi air to-secure rapid and corhplete reaction; I

The "ferric iron alreadyin the ore;v as well" as that produced by the oxidationof the ferrous iron react with titanium tetrachloride according: to Equation- 2', supra, fromwhich it is apparent that 1 .78 parts 015 titanium tetrachloride are required forthe conversion of impart of ferric oxide in' the oxidized ore to' ferric chloride;:or differently expressed, l.32.part's of titanium tetrachloride will be necessary to convertv eachip'art of ferrous oxide and 1.78 parts of titanium tetrachloride for each p'art of ferric oxide in the original ore.

Treatment of the'oxidized ore by titanium tetrachloride gas is preferably carried outby formingza flui'di'zed bed of theoxidized ore in a reactorbypassing titanium tetrachloride: gas, which: maybemixed with an inert non-re-- ducing gas such as: nitrogen,-upwardly through the oreat a space gas velocity of between 0.3 foot per second and 1.0 foot per s'econdl To this liuidized -be'd additional oxidized ore is added as the ieaction' goesiforward at an elevated temperature to produce volatilized ferric chloride and substantially pure titanium dioxide.

The amount of titanium tetrachloride used for eflicient and economical operation is preferably the theoretical amount required to react with the oxygen values of the iron in the ore although a slight excess of the stoi'chiom'etric amount of titanium tetrachloride will insure high conversions of the ironvalues.

An inert gas such as, 'for example; nitrogen may be mixed withthe titanium tetrachloridein the ratioof about 1 part of titanium tetrachloride to about 1, part of nitrogen which is used primarily tbhelp sustain the fluidized bed, and: to'facilitate regulation of the ratio (if-titanium tetrachloride' to ore being, fed tothe reactor; However, where such considerations are not paramount, the titanium tetrachloride alone maybe used successfully. The temperature for chlorination of the iron-valuesby'the titanium tetrachloride (and nitrogen) is preferably between about 850 C. and about 1050 C. at which temperatures and, in particular, the higher temperatures the efliciency of the reaction may be expected to be as high as 98.5%.

In this connection, the heat necessary to maintain the hereinabove described reactions at their most eflicient operating temperatures may, for small installations such as pilot plant installations, be supplied by electric resistance elements wrapped around or otherwise intimately associated with the reactor of the apparatus. In the case of large commercial installations, heat generated by an exothermic reaction within the reactor may be relied upon, in large measure, to maintain the reaction for continuous operation.

Thus by the improved and economical method of this invention, titaniferous iron ores may be treated by oxidation and chlorination to separate out volatile ferric chloride from the ore and leave a residue of substantially pure titanium dioxide.

The following examples are presented to explain more fully the details of a preferred embodiment of this invention.

Example I 5,529 parts, more or less, of finely divided raw titaniferous iron ore analyzed as comprising 58.6 parts of titanium dioxide, 22.4 parts ferric oxide and 13.5 parts ferrous oxide and having particle sizes of the order of 48150 mesh were preheated to substantially 300 C. and added at the rate of substantially 34 parts, more or less, per minute into the upper portion of a reaction chamber in which a fluidized bed, between about to 36 inches in height, and containing susbtantially 1,805 parts, more or less, of beneficiated titaniferous ore was maintained. The beneficiated titaniferous ore of the fluid bed had a particle size of the order of 48-150 mesh. The fluidized bed was maintained by passing a gaseous mixture in the ratio of between about 2.7 to 0.9 parts titanium tetrachloride to about 1 part chlorine in an upward through the constituents of theflu-idized bcdat the'rate ofsubstantially 0.35 foot per second and preheated to substantially 300 C. The temp'e'rature'of' the bed was maintained at about 1050- C. The: tit'aniferous residue was withdrawn: from the reactor at the rated between: about 23- parts to about 30'pa-rts per minute and contained? substantially titanium dioxide and: 6.6% iron-oxide, the balance being siliceous. gan-gue and the like; The reaction was continued for a period of 2 hours under substantially steady state conditions and a total of substantially 4 ,622 .parts, more or less, of titanium-residue was obtained.

The eificiency of the reaction was computed on the basis of the number of parts of titanium tetrachloriderequired theoretically toreplace all the: chlorin'atable elements per parts of ore. On this basis the cal culated required titanium tetrachloride: was substantially 2,795 parts while the actual titanium tetrachloride used:- in' the experiment was susbtantially 2,873 parts. The overall efi'i'ciency'of the reaction was therefore 97.5%

Example 11 The procedure used in Example I was repeated except that the raw ilmenite ore added to the reactor was re placedby an ilmenite ore which contained substantially 25:9% iron: and which had been: oxidized by roastingirr the'prese'nce of air until substantially all of the iron was. converted to the ferric state, the percentage of iron remaining in the ferrous state being as low as about-1 .67%. A- 'benefi'ciated titaniferous iron ore bed was maintained by-jp'assing a mixture of titanium tetrachloride and nitro-: gen in theratio of about 1 part of titanium'te'trachloride to about 1- p'artnitrogemat the rate of substantially- 0135' foot per second and preheated to substantially 300 in an upward flow through the bed, the temperature of which was heldat substantially 1050 C. Additional oxidizcd-ore preheated to about 300 C. was added at the rate of about 42 parts per minute, more or less,- and the-titaniferous residue was withdrawn from the reactor at the rate of about 30 parts per minute, more or less. The residue contained substantially 87.5% titanium dioxide and 6.02% iron oxide, the balance being siliceous gangue and the like.

The reaction proceeded smoothly throughout the run with no evidence of the formation of ferrous chloride, nor was there any evidence of plugging or sintering of the fluid bed.

Example III 2,260 parts, more or less, of finely divided reduced titaniferous iron ore analyzed as comprising 74.1 parts of titanium dioxide, 5.8 parts ferric oxide, and 20.9 parts ferrous oxide was added at the rate of substantially 35 parts per minute to a fluidized bed at a temperature of substantially 875 C. The gas space velocity of the fluidized bed was substantially 0.31 foot per second and was maintained by adding gaseous titanium tetrachloride at the rate of substantially 13.2 parts per minute and gaseous chlorine at the rate of substantially 5 parts per minute, the mixture of gaseous titanium tetrachloride and chlorine being the theoretical amount to react with the given quantity of ore to yield vaporous ferric chloride and titanium dioxide. The run was continued for substantially one hour and twenty minutes under substantially steady state conditions. The titanium residue contained substantially 97.8% titanium dioxide and 3.2 iron oxide, the overall efiiciency of the titanium tetrachloride reaction based on iron and other chlorinatable products removed from the reduced ore being substantially 98.2%. It was noted that the reaction could be run successfully at lower temperatures than 875 C. and conversions have been obtained at temperatures as low as 500 C.

By use of the improved and integrated process of this invention, an unusually high conversion of the iron, in a titaniferous iron material, to volatile ferric chloride has been obtained with substantially no contamination by titanium values, while the resulting titanium dioxide product has been substantially pure and in a granular form susceptible to chlorination. Moreover, by using the improved and integrated ore treating process of this invention, iron may be separated from raw titaniferous iron ore on a commercial scale with a high degree of efiiciency to produce a volatile substantially uncontaminated ferric chloride which is substantially free of carbon or carbon-containing gases and which may be subsequently oxidized, if desired, to produce chlorine for recirculation through additional raw ore; and a stable titanium residue which is substantially pure titanium dioxide and which may be subsequently chlorinated to produce titanium tetrachloride. Furthermore, by the improved process of this invention, titaniferous iron materials in which substantially all of the iron values are in, or have been converted to, the ferric state may be directly chlorinated to form volatile ferric chloride, the constituents being used to their full advantage and with a minimum of handling with the result that the process is characterized by high yields which are substantially free of the unrecoverable losses inherent in processes heretofore known and used.

While this invention has been described and illustrated by the examples shown, it is not intended to be strictly limited thereto and other modifications and variations may be employed within the limits of the following claims.

We claim:

1. A method for separating the iron values from the titanium values in a titaniferous iron ore containing both ferrous and ferric iron which comprises treating said ore with an oxidizing agent and titanium tetrachloride in the absence of a reducing agent at a temperature of at least 500 C. to form volatilized ferric chloride and titanium dioxide, said titanium tetrachloride being added in substantially the stoichiometric amount to react with the iron values to form iron chloride and titanium dioxide,

said oxidizing agent being added in amount to oxidize the ferrous iron values to ferric iron.

2. A method according to claim 1 in which the temperature is from about 850 C. to about 1050" C.

3. Method according to claim 2 in which said oxidizing agent employed is chlorine gas.

4. A method for separating the iron values from the titanium values in a titaniferous iron ore containing both ferrous and ferric iron which comprises forming a fluidized bed of said ore, treating said ore with chlorine gas and titanium tetrachloride in the absence of a reducing agent at a temperature of at least 500 C. to form volatilized ferric chloride and titanium dioxide, said titanium tetrachloride being added through said bed in substantially stoichiometric amount to react with the iron values to form iron chloride and titanium dioxide, said chlorine being added through said bed in an amount to oxidize the ferrous iron values to ferric iron.

References Cited in the file of this patent UNITED STATES PATENTS 1,528,319 Carteret et al Mar. 3, 1925 1,845,342 Saklatwalla Feb. 16, 1932 2,183,365 Booge Dec. 12, 1939 2,184,884 Muskat Dec. 26, 1939 2,494,337 Hemminger Jan. 10, 1950 2,589,466 Wilcox Mar. 18, 1952 2,621,118 Cyr et al. Dec. 9, 1952 FOREIGN PATENTS 587,774 Great Britain May 6, 1947 OTHER REFERENCES Mellors Comprehensive Treatise on Inorganic and Theoretical Chemistry, vol. 7, published by Longmans, Green & Co., 1927, page 82.

Wilcox application S. N. 690,613, filed August 16, 1946, now abandoned (cited as such in the above cited Wilcox patent). 

1. A METHOD FOR SEPARATING THE IRON VALUES FROM THE TITANIUM VALUES IN A TITANIFEROUS IRON ORE CONTAINING BOTH FERROUS AND FERRIC IRON WHICH COMPRISES TREATING SAID ORE WITH AN OXIDIZING AGENT AND TITANIUM TETRACHLORIDE IN THE ABSENCE OF A REDUCING AGENT AT A TEMPERATURE OF AT LEAST 500* C. TO FORM VOLATILIZED FERRIC CHLORIDE AND TITANIUM DIOXIDE, SAID TITANIUM TETRACHLORIDE BEING ADDED IN SUBSTANTIALLY THE STOICHIOMETRIC AMOUNT TO REACT WITH THE IRON VALUES TO FORM IRON CHLORIDE AND TITANIUM DIOXIDE, SAID OXIDIZING AGENT BEING ADDED IN AMOUNT TO OXIDIZE THE FERROUS IRON VALUES TO FERRIC IRON. 